Privately held One Lambda's diagnostic tests are used by transplant centers mostly to determine the compatibility of donors and recipients before a transplant occurs. They are also used to detect the presence of antibodies that can lead to transplant rejection.

The Canoga Park, Calif., company was founded in 1984 and has about 320 workers. Its 2011 revenue was $182 million.

"With its strong technology platform, high margin profile and good growth prospects, the business is perfectly aligned with our specialty in vitro diagnostics strategy," Thermo Fisher President and CEO Marc Casper said in a statement.

The transaction includes a three-year retention program created by One Lambda for key employees, amounts payable to certain shareholders for noncompetition agreements and a one-year provision for additional payments if certain financial targets are met.

Thermo Fisher plans to finance the acquisition with available cash and new debt financing.

The deal is expected to immediately add to Thermo Fisher's earnings. It is anticipated to add 9 cents to 11 cents per share to Thermo Fisher's 2013 adjusted earnings.

The acquisition is expected to close in the fourth quarter, at which point One Lambda will join Thermo Fisher's specialty diagnostics unit.

In addition, Thermo Fisher said Monday that its board approved the repurchase of an additional $500 million shares of its common stock. The Waltham, Mass., company had $250 million remaining under an existing buyback as of June 30. That program expires on Nov. 9.

The new repurchase program is effective through Dec. 31.

Shares of Thermo Fisher edged up by a penny to $52.05 in afternoon trading. Its shares are up 21 percent since their 52-week low of $43.06 in mid-December. They peaked for the past year at $66.30 last July.